An organic light-emitting diode (OLED) display, also known as an organic electroluminescent display, is an emerging flat panel display device. Because its advantages of simple preparation process, low cost, low power consumption, high light-emitting brightness, wide operating temperature adaptation, small size, and fast response. It is easy to realize color display and large-screen display, match an integrated circuit driver, and realize a flexible display. It has broad application prospects.
With the development of display technology, a transparent display device is proposed as a novel display device. The transparent display device can not only see the displayed image from the front of the screen, but also can see the object on the back of the transparent display through the screen. Transparent displays have a lot of possible applications such as buildings, windows of cars, and display windows for shopping malls. Besides the applications of these large devices, small devices such as hand-held tablets can benefit from the transparent displays. A lot of the existing display markets are expected to be replaced by the transparent displays. For example, they can be in the fields of construction, advertising, and public information.
FIG. 1 is a cross-sectional view of a conventional transparent OLED display. FIG. 2 is a plan structural view of a sub-pixel region of the transparent OLED display shown in FIG. 1. The transparent OLED display includes a display region and a peripheral region around the display region. The display region includes a plurality of sub-pixel regions. Referring to FIG. 2, each sub-pixel region includes an opaque thin film transistor (TFT) region, an opaque storage capacitor (Cst) region, and a transparent region other than the TFT region and the Cst region. Referring to FIG. 1, the transparent OLED display includes a base substrate 100, a first metal layer 200 disposed on the base substrate 100, a gate insulating layer 300 disposed on the base substrate 100 and covering the first metal layer 200, an active layer 400 disposed on the gate insulating layer 300, an etching stop layer 500 disposed on the gate insulating layer 300 and covering the active layer 400, a second metal layer 600 disposed on the etching stop layer 500, a passivation layer 700 disposed on the etching stop layer 500 and covering the second metal layer 600, a flat layer 800 disposed on the passivation layer 700, an anode layer 910 disposed on the flat layer 800, a pixel defining layer 940 disposed on the flat layer 800 and the anode 910, an opening 945 disposed on the pixel defining layer 940 and corresponding to a top of the anode 910, an OLED light-emitting layer 950 disposed in the opening 945 and located on the anode 910, and a cathode 960 disposed on the OLED light-emitting layer 950 and the pixel definition layer 940.
The first metal layer 200 includes a gate 210 and a first storage capacitor electrode 220 disposed at intervals. The second metal layer 600 includes a source 610, a drain 620, and a second storage capacitor electrode 630 disposed at intervals.
The gate 210, the active layer 400, the source 610, the drain 620, the anode 910, the OLED light-emitting layer 950 and the cathode 960 are located in the TFT region. The first storage capacitor electrode 220 and the second storage capacitor electrode 630 are located in the Cst region. Since the first storage capacitor electrode 220 and the second storage capacitor electrode 630 are both made of a metal material, the Cst region is not light-transmitting. The Cst region has a larger area and wastes a certain light-transmitting area and aperture ratio so it reduces the transparent display effect of the OLED display. In addition, during the preparation of the transparent OLED display, a terminal (pad) 930 located in the peripheral region are usually made of the same material as that of the anode 910 in the same process. Both the terminal 930 and the anode 910 are composite layers including two layers of indium tin oxide (ITO) film 931 sandwiching a layer of silver thin film 932. Since the terminal 930 is located in the peripheral area of the transparent OLED display and exposed to the external environment, it is easy to contact the water and oxygen. As a result, the silver thin film 932 is corroded to affect the electrical properties and service life of the terminal 930.